information on the hydrocarbon-type composltion of gasoline is required for continued research on Internal combustion engines, including efforts to Improve efficiency and reduce emissions. The standard method for obtainlng thls Information Is based on liquid chromatography and has been used for many years. An Improved technlque of greater precision was sought that would require less analysis time, whfle serving as an independent method of anaiysls. A nuclear magnetic resonance (NMR) technique has been developed for determlnlng the composltion (aromatlc, parafflnic, and oleflnlc) and hydrogenharbon ratio of gasoline. The equations requlred for the caiculatlons are derived. Results from the NMR method on 36 commerclai gasoiines are presented along with the results from the more familiar fluorescent indicator adsorption (FIA) method and the combustion method. The absolute standard devlations between the NMR and FIA methods are l.Q%, 3.2%, and 2.4% for the aromatics, paraffins, and olefins, respectively. A standard deviation of 0.055 is obtained on hydrogen/carbon ratios, Gasolines, which are complex mixtures of several hundred compounds, are usually characterized by hydrocarbon type rather than by complete analysis. Hydrocarbon types are usually determined by the fluorescent indicator adsorption (FIA) method. This method is a liquid chromatographic technique which separates the sample on silica gel into aromatic, paraffinic, and olefinic components. The FIA method is described fully in ASTM Method D-1319 ( 1 ) . The need for a rapid, independent technique of greater precision has been recognized for some time.High resolution NMR is a potentially useful tool f?r the analysis of petroleum mixtures, such as gasoline (2-4), because they are rich in hydrogen atoms which provide Ztrong ' proton NMR signals. The principles of NMR spectrometry utilized in such an analysis are described (5-7).As the FIA method provides a chromatographic separation of the three hydrocarbon types, the NMR method provides the spectrometric measurement of the three hydrocarbon types without separations. One purpose of this paper is to describe how to interpret the NMR spectrum of a gasoline to obtain a quantitative measure of the three hydrocarbon types (aromatic, paraffinic, and olefinic) present in the sample. The second purpose of this paper is to show how the equations derived for the hydrocarbon-type distribution can be easily rearranged to yield the hydrogen/carbon ratio.

No abstract